1. Field of the Invention
The invention relates to a signal converting device, more particularly a voltage-to-digital converting device having a voltage-to-time converter.
2. Description of the Related Art
A conventional voltage-to-time converter proposed in an article by J.-B. Begueret, M. R. Benbrahim, Z. Li, F. Rodes and J.-P. Dom, entitled “Converters dedicated to long-term monitoring of strain gauge transducers”, IEEE JSSC, vol. 32, pp. 349-356, March 1997, is capable of converting a voltage signal into a timing signal that is associated with resistance and capacitance of an RC-integrator. However, a drift of integrated circuit fabrication easily incurs an error in the capacitance of the RC-integrator. Furthermore, increased operating temperature may cause the resistance of the RC-integrator to vary. Therefore, due to non-ideal variance of the resistance, resolution of the timing signal generated by the conventional voltage-to-time converter is reduced.
Another conventional voltage-to-time converter proposed in an article by S.-J. Bae, H.-J. Chi, Y.-S. Sohn and H.-J. Park, entitled “A VCDL-based 60-760 MHz dual-loop DLL with infinite phase-shift capability and adaptive-bandwidth scheme”, IEEE JSSC, vol. 40, pp. 1119-1129, May 2005, is capable of outputting a timing signal in response to an input voltage, where the timing signal has a time delay corresponding to the input voltage. However, the conventional voltage-to-time converter is based upon non-linear operation, i.e., the time delay is not proportional to the input voltage.